The disclosed technology relates to oligomeric or polymeric phosphites and their use in lubricant formulations, including lubricants for driveline applications.
Phosphorus esters of various types are well known for their use as lubricant additives. For example, U.S. Pat. No. 6,730,640, Sowerby et al., May 4, 2004, discloses a method for lubricating a continuously variable transmission. The lubricant is a fluid composition which comprises an oil of lubricating viscosity and an oil-soluble zinc salt, which may be a zinc hydrocarbyl phosphate. The zinc hydrocarbyl phosphate can be prepared by reacting phosphorus acid or anhydride with an alcohol, followed by neutralization with a zinc base. The alcohols may be monohydric alcohols, or polyhydric alcohols such as alkylene polyols such as ethylene glycols, including di-, tri- and tetraethylene glycols; propylene glycols, including di-, tri- and tetrapropylene glycols; glycerol; and the like. Additional additives may also be present, such as other friction modifiers and phosphorus-containing antioxidants.
U.S. Pat. No. 4,557,845, Horodysky et al., Dec. 10, 1985, discloses products of reaction between a 2-hydroxyalkylalkylamine or certain higher oxylated members, and a dihydrocarbyl phosphite as friction reducers and fuel reducing additives for internal combustion engines when such products are compounded with lubricant and liquid fuels. Among the reaction products are compounds such as
where R is a C6 to C30 hydrocarbyl group.
U.S. Pat. No. 4,298,481, Clarke, Nov. 3, 1981, discloses high temperature grease composition which contains a load bearing component. Useful load-bearing additives include polyphosphates including those of the structure(R1O)(R2O)P—OR3O——O—P(OR4)—OR5O—n—P(OR6)(OR7)[sic]R3 and R5 are polyalkylene glycol, alkylidene bisphenol, hydrogenated alkylidene bisphenol, or ring-halogenated alkylidene bisphenol from which the two terminal hydrogens have been removed; n is an integer in the range of 1 to 18.
U.S. Pat. No. 4,704,218, Horodysky et al., Nov. 3, 1987, discloses the reaction products of long chain vicinal diols containing at least 10 carbon atoms and one or more sulfur atoms in the chain, with a dihydrocarbyl hydrogen phosphate containing 1 to 6 carbon atoms in each hydrocarbyl group, as effective friction-reducing antiwear additives in lubricating oils, greases and fuels.
U.S. Pat. No. 5,968,880, Mathur et al., Oct. 19, 1999, discloses lubricating compositions and a metal-free thiophosphorus acid ester which contains at least one hydrocarbyl terminated oxyalkylene group or hydrocarbyl terminated polyoxyalkylene group. The ester may be represented by the formula(R1—(OR2)x—X2)3-a—P(═X1)—(X3R3)a where R1 is a hydrocarbyl group, R2 is an alkylene group, and R3 is hydrogen or a hydrocarbyl group. Also disclosed are salts of such thiophosphorus acid esters, including amine salts, e.g., hydroxylamine salts.
U.S. Pat. No. 6,103,673, Sumiejski et al., Aug. 15, 2000, discloses compositions containing friction modifiers for continuously variable transmissions, which include at least 0.1 percent by weight of at least one phosphorus compound. The phosphorus compound can be a phosphorus acid or ester of the formula (R1X)(R2X)P(X)nXmR3 where R1, R2, and R3 are hydrogen or hydrocarbyl groups. R1 and R2 groups can comprise a mixture of hydrocarbyl groups derived from commercial alcohols, examples being monohydric alcohols.
Other patents with related disclosures include U.S. Pat. No. 6,528,458, Tagliamonte et al., Mar. 4, 2003; U.S. Pat. No. 6,451,745, Ward, Sep. 17, 2002, and U.S. Pat. No. 6,251,840, Ward et al., Jun. 27, 2001.
U.S. Pat. No. 4,163,767, Giolito, Aug. 7, 1979, disclose a polyphosphorous mixed phosphite-phosphonate polymer flame retardant, especially for urethane foams.
One problem encountered with low molecular weight phosphites such as dialkyl (e.g., dibutyl) phosphites (sometime referred to as dialkyl hydrogen phosphites) is that they may readily absorb into elastomeric seals where they may subsequently lead to acid formation causing degradation of the seal material. The disclosed technology provides higher molecular weight, oligomeric or polymeric phosphites which provide phosphorus and consequent antiwear performance properties to lubricant formulations, while providing a lubricant having at least one of the properties of reduced degradation of elastomeric seals, reduced odor, reduced toxicity, reduced volatility, and reduced corrosion.